The California state legislators who will vote by Friday on a high-speed rail program are leaning on a potentially unreliable federal government.

In theory, California High-Speed Rail Authority planners anticipate receiving more than $41 billion in federal funds through the year 2026. In practice, the money might be harder to come by than the federal funds already in hand.

Congressional Republican opposition now seems locked into party doctrine. Mitt Romney, the presumptive GOP presidential candidate, has sounded skeptical. A crushing federal debt will constrict future spending, and all of this complicates a project that’s depending on the federal government for the bulk of its budget.

“In light of the federal government’s trillion-dollar budget deficits, there is no money for a lot of things, including the poorly planned, massive boondoggle of high-speed rail,” Rep. Devin Nunes, R-Visalia, Calif., said Thursday.

For the short run, California high-speed rail planners have the federal money they need. The $3.3 billion provided by the Obama administration is enough to help build the initial 130-mile section from Bakersfield to Madera, if the Legislature approves an additional $2.7 billion from state bond funds.

The federal dollars came from Obama’s stimulus package, secured in 2009 while Democrats still controlled Congress.

For the longer run, the state’s latest business plan relies on continuing federal aid to complete a Los Angeles-to-San Francisco project now slated to cost $68 billion. Starting in 2015, the business plan expects annual federal contributions that range from $2.2 billion to $3.8 billion.

“As the program proceeds, the state will continue to see significant federal support and private-sector capital investment once operations have commenced,” the revised business plan states.

In an interview earlier this year, California High-Speed Rail Authority Chairman Dan Richard said state officials “do not expect any additional federal funds for the next three years,” after which Republican resistance may soften.

“It’s unfortunate that high-speed rail has become a high-profile political project,” Richard said, “and I hope in the future it will revert to being just another transportation alternative.”

The extent of that future federal support is now one of the questions being investigated by the non-partisan Government Accountability Office. Republican lawmakers initially requested the study and are actively undercutting the support.

By a 239-185 margin, with only two Republicans defecting, the House on June 29 approved an amendment that blocks new Fiscal 2013 transportation funds from supporting California’s rail project. Although the House funding package already omitted high-speed rail dollars, the amendment ensured highway funds couldn’t be transferred to rail. More to the point, it flashed a big red light.

“We need to make sure that our gas tax dollars get used for their intended purpose of actually improving our roads and highways,” said the amendment’s author, Rep. Jeff Denham, R-Turlock, Calif.

Democrats pounced, with Rep. John Garamendi, D-Walnut Grove, Calif., contending the amendment “imperils” other California transit projects. Members of the California High-Speed Rail Caucus called it “thoughtless partisanship,” but its approval continued a pattern. Earlier this year, the House Transportation and Infrastructure Committee approved a similar Denham amendment on a separate surface transportation bill.

The final version of the surface transportation bill, to be signed Friday by President Barack Obama, omitted the Denham high-speed rail language.

Still waiting in the wings is another signal-sending bill to freeze California high-speed rail spending authored by House Majority Whip Kevin McCarthy, R-Bakersfield, Calif. The House Appropriations Committee likewise blew off Obama’s request for high-speed railing funding, with the committee’s official report sniping at “unrealistic new high-speed rails to nowhere.”

Obama has not backed away from his support, setting the stage for continued fights with Congress. Although Romney has apparently not taken a clear-cut position on high-speed rail, the former Massachusetts governor was quoted by the Tampa Bay Times last year as saying that “sometimes these transit projects look great until you have to subsidize them for decades.”

California rail planners say that if Congress clams up, “cap-and-trade” funds provided by polluters’ fees could also be tapped. The total fees could range between $660 million and $3 billion annually, according to the state Legislative Analyst’s Office, but high-speed rail would have to compete with clean energy, natural resource protection and other environmentally friendly projects for a slice of the pie.